Background/Purpose: Biosimilar infliximab offers a potentially lower‐cost treatment option compared to its bio‐originator. However, uptake of biosimilars in general in North America has been slow. To describe new users of infliximab in the US, comparing biosimilar and bio-originator, in terms of missed doses and discontinuation.

Methods: We used from data Marketscan® Commercial Claims and Encounters and the Medicare Supplemental and Coordination of Benefits databases (January 1^st, 2017 to December 31^st, 2018). We studied adult individuals (age>18 years), who were infliximab-naïve (new users). The date of first infliximab claim was defined as the index date. We assessed i) first missed dose and, ii) occurrence of complete discontinuation. Missed dose was defined as any gap between infusions beyond recommended intervals (0, 2, and 6 weeks during the induction phase and 8 weeks in the maintenance phase). If there was no record of an infliximab infusion at the expected date of the next injection (plus a grace period of 7 days), a discontinuation event was assigned.

Results: In the new-user cohort there were 5,596 new users of infliximab, including 301 biosimilar users. Baseline characteristics of individuals included in the analysis are shown in Table 1. Among patients initiating treatment with infliximab biosimilar, 30.9% missed at least one scheduled infusion during the induction phase, similar to the percent (28.6%) among the originator infliximab users. After multivariable adjustment for age, sex, date of treatment initiation, medication use (other biologic medications, synthetic DMARDs, and corticosteroids), and underlying diseases, we were unable to detect if first missing dose in the induction phase differed between the two groups (adjusted hazard ratio, aHR = 1.14; 95% CI = 0.92-1.41). For patients completing the induction phase (n=3,282), 33.1% of biosimilar users missed at least one infusion within one year during the maintenance phase, which was not statistically different from the originator users (40.1%). The adjusted analysis showed no clear difference for first missed dose between groups (aHR = 0.94, 95% CI =0.71;1.24). Complete discontinuation in the maintenance phase (a gap more than 90 days beyond the expected infusion date without restarting therapy), was similar in the biosimilar group (13.1%) and originator group (15.5%). In adjusted analysis, we were unable to show significant difference among groups for complete discontinuation (aHR = 1.00, 95% CI =0.63;1.59)

Conclusion: Biosimilar infliximab use in the United Sates continues to be low over 2017-2018. In new users, we were unable to detect differences between biosimilar and bio-originator, in terms of missed doses and discontinuation.

Table 1 – Baseline characteristics of new users of infliximab biosimilar and infliximab originator, Marketscan, 2017-2018.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/recent-use-missed-doses-and-discontinuation-of-infliximab-in-new-users-comparisons-of-biosimilar-and-originator-exposures/